On 06/01, Chao Yu wrote: > [1] > https://www.mail-archive.com/[email protected]/msg15126.html > > As [1] reported, if lower device doesn't support write barrier, in below > case: > > - write page #0; persist > - overwrite page #0 > - fsync > - write data page #0 OPU into device's cache > - write inode page into device's cache > - issue flush
Well, we have preflush for node writes, so I don't think this is the case. fio.op_flags |= REQ_PREFLUSH | REQ_FUA; > > If SPO is triggered during flush command, inode page can be persisted > before data page #0, so that after recovery, inode page can be recovered > with new physical block address of data page #0, however there may > contains dummy data in new physical block address. > > Then what user will see is: after overwrite & fsync + SPO, old data in > file was corrupted, if any user do care about such case, we can suggest > user to use STRICT fsync mode, in this mode, we will force to trigger > preflush command to persist data in device cache in prior to node > writeback, it avoids potential data corruption during fsync(). > > Signed-off-by: Chao Yu <[email protected]> > --- > v2: > - fix this by adding additional preflush command rather than using > atomic write flow. > fs/f2fs/file.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > index 7d5311d54f63..238ca2a733ac 100644 > --- a/fs/f2fs/file.c > +++ b/fs/f2fs/file.c > @@ -301,6 +301,20 @@ static int f2fs_do_sync_file(struct file *file, loff_t > start, loff_t end, > f2fs_exist_written_data(sbi, ino, UPDATE_INO)) > goto flush_out; > goto out; > + } else { > + /* > + * for OPU case, during fsync(), node can be persisted before > + * data when lower device doesn't support write barrier, result > + * in data corruption after SPO. > + * So for strict fsync mode, force to trigger preflush to keep > + * data/node write order to avoid potential data corruption. > + */ > + if (F2FS_OPTION(sbi).fsync_mode == FSYNC_MODE_STRICT && > + !atomic) { > + ret = f2fs_issue_flush(sbi, inode->i_ino); > + if (ret) > + goto out; > + } > } > go_write: > /* > -- > 2.29.2 _______________________________________________ Linux-f2fs-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
